Testing blade sharpness with paper?

[Frederick Skelly]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

[chris carter]

I find paper not reliable because there's a skill aspect to it. I used to have fun testing my pocket knife on paper and there's a technique to how you hold the paper and how you draw the knife through it that can have WILD implications on making it remarkably easier.

For plane irons I just set the edge of the iron on my fingernail. If it slides with gravity, it's not sharp. If it catches, then it's sharp.

[Mel Fulks]

Agree that it is not good test. But paper usually has a grain that makes the test easier with the right edge choice.

[Steven Mikes]

I'm a paper tester... I find only 25° bevel will push through without any slicing motion. Usually add a little slice in the motion to get it going. Also have to hold the paper behind the cut to keep it it tension. Not as hard as it sounds, and I can easily feel if there are spots on the blade that I missed based on if and where it catches on the paper.

Also like the shaving wrist hair test

[John K Jordan]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

I sometimes test with paper when I sharpen knives. I keep a pad of PostIt notes, hold one sheet in the left hand, and push the blade into the paper. (I don't think I slice but I'll have to pay more attention next time.) My knife edge quality went way up when I got a Realsharp sharpener. I joke that the knife will slice paper dropped onto the blade but that's an exaggeration!

I don't test chip carving knives this way. After going through the four grits using the MyChipCarving sharpening kit (15 micron, 9 micron, 5 micron, 3 micron) the edge is always incredibly sharp. (On a chip carving knife you only use a short bit of the edge anyway, right at the point.)

JKJ

[Tom M King]

I quit testing a long time ago.

[Jim Koepke]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

Hi Fred,

The paper test is a bit tricky. It takes a very sharp blade and as mentioned already keeping the right tension between the blade and the paper. Also the lighter the paper, the sharper the blade needs to be. As mentioned paper has grain. It is usually aligned with the long direction of a sheet of paper.

Another part of the equation is as Steven said about the angle of the bevel having an influence on the results.

Also, many people find sharp is a moving target. Over time your sharpening will likely be able to pull 0.001" shavings. Your first sub thou shaving will be an exciting event.

Thin shavings seem to have a mesmerizing effect on me.

Here is one being measured after a smoother was sharpened:

Oops, the wrong image was uploaded and then removed from the body of text. It is now an attachment below.

Here is the correct image:

Fine Shaving 0.0002x?.jpg

This indicates a shaving of ~0.00025". This is still a fat shaving compared to what they do in the Japanese Kezuroukai competition.

Most of the time if my blades can cleanly pare end grain that is good enough to put to work.

One test is shaving arm hair. This is can be dangerous, especially with chisels smaller than 3/8". Some have even become upset that it is mentioned. The feel of the blade removing hair is an indicator of sharpness. Razor sharpeners use an even finer test with a hanging hair. If a blade seems to pull the hair, it is not sharp enough for cutting paper. My preference is to have a clean swath of hair removal without being able to feel the blade doing its work.

jtk

[ken hatch]

I quit testing a long time ago.

Yep, same here. If it looks sharp and feels sharp it is sharp.

ken

[Pat Barry]

If you can't cut paper its not sharp enough.

[Rob Luter]

I check on my thumbnail. The process I use always gives predictable results. I don't get wrapped up in shaving thickness as much as surface quality. Whether the shaving is .002 or .004 isn't that important to me.

[Frederick Skelly]

Thanks guys!
Jim, that sub-thou shaving is mighty impressive!

Fred

[Robert Hazelwood]

I'd say if you can sharpen well enough to pare pine end grain and take decent shavings, as you say, then there's not much need to test, just get to work. You can almost certainly get sharper than you are now, but it will come with time and experience.

That said, for some reason it is more awkward to slice paper with a plane iron or chisel than with a pocketknife. I could always do it easily with a knife- even an edge I'd consider a bit dull can still slice printer paper; sharp ones could easily do phonebook paper. But a plane iron that I know is just as sharp is difficult, or it least it was the last time I tried. It will eventually cut but you have to figure out the angle to hold it. I think the asymmetric (chisel) grind of woodworking tools is one reason it's harder.

[Doug Hepler]

Frederick

Shavings from end grain is a "real" test, but you have to reassemble the plane to test it. Arm hair and paper are much more convenient. When I run out of arm hair I use paper. Any paper will do, but I kept an LLBean catalog for this purpose. Take a new single-edge razor blade or the equivalent and try the paper test with it. That will pretty much set the standard for you. I usually have to slice a bit to get the edge in the paper. Then I try pushing without slicing. If that does not cut the paper I judge the sharpness by how much I need to slice and how hard I have to push. When an edge pases the paper test I put it back in the plane and try it out. It is almost always satisfactory.

The thread test is probably more repeatable than paper, and almost as convenient. A step up from that (or is it down, into obsession?) is a maximum force gauge. You can google both of these. Straight razor aficionados post about these fairly often.

As others have hinted, we can easily become obsessive with sharpness as an end rather than a means. That perfect "80 gram" edge won't last for many cuts in hardwood.

Doug

[John K Jordan]

The thread test is probably more repeatable than paper, and almost as convenient. A step up from that (or is it down, into obsession?) is a maximum force gauge. You can google both of these. Straight razor aficionados post about these fairly often.

Are you referring to the Sharp Check? (Sorry if this was written earlier, I didn't read the entire thread.) It measures the force needed to cut through a calibrated monofilament thread.

I have the PT50 model and it is extremely repeatable. We've used it on knives as intended but also on several lathe tools. I want to try it on card scrapers too if I can rig up an way.

Sharp_Check.jpg

http://www.edgeonup.com/eou_new_2016_004.htm

JKJ

[Brian Holcombe]

Test it on the wood.